System and Method Using a Microwave-Transparent Reaction Chamber for Production of Fuel from a Carbon-Containing Feedstock

ABSTRACT

Approaches for producing fuel from a carbon-containing feedstock are described. Feedstock is introduced into a substantially microwave-transparent reaction chamber. A microwave source emits microwaves which are directed through the microwave-transparent wall of the reaction chamber to impinge on the feedstock within the reaction chamber. The microwave source may be rotated relative to the reaction chamber. The feedstock is subjected to microwaves until the desired reaction occurs to produce a fuel. A catalyst can be mixed with the feedstock to enhance the reaction process.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/854,754, filed Aug. 11, 2010, which claims the benefit of ProvisionalPatent Application Ser. No. 61/233,694, filed on Aug. 13, 2009, to whichpriority is claimed pursuant to 35 U.S.C. §119(e) and which are herebyincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to the production of fuel from acarbon-containing feedstock.

BACKGROUND OF THE INVENTION

The vast majority of fuels are distilled from crude oil pumped fromlimited underground reserves. As the earth's crude oil supplies aredepleted, the world-wide demand for energy is simultaneously growing.Over the next ten years, depletion of the remaining world's easilyaccessible crude oil reserves will lead to a significant increase incost for fuel obtained from crude oil.

The search to find processes that can efficiently convert renewablematerials to fuels suitable for transportation and/or heating is animportant factor in meeting the ever-increasing demand for energy.Methods and systems for efficiently converting carbon-based feedstockssuch as biomass into liquid fuel are needed. The present inventionfulfills these needs and provides various advantages over the prior art.

SUMMARY OF THE INVENTION

Embodiments of the present are directed to a system for producing fuelfrom a carbon-containing feedstock. The system includes at least onereaction chamber comprising at least one microwave-transparent chamberwall and a reaction cavity configured to hold the carbon-containingfeedstock. A microwave subsystem includes at least one device configuredto emit microwaves when energized. The microwave device is positionedrelative to the reaction chamber so that the microwaves are directedthrough the microwave-transparent chamber wall and into the reactioncavity. The system also includes a mechanism that provides relativemotion between the microwave device and the reaction chamber.

Another embodiment of the invention involves a process for converting acarbon-containing compound to fuel. A carbon-containing feedstock isinput into a substantially microwave-transparent reaction chamber.Microwaves are directed from a microwave source through walls of thereaction chamber to impinge on the feedstock. The feedstock ismicrowaved until it reacts to produce a fuel.

The above summary is not intended to describe each embodiment or everyimplementation of the present invention. Advantages and attainments,together with a more complete understanding of the invention, willbecome apparent and appreciated by referring to the following detaileddescription and claims taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B illustrate side and cross sectional views, respectively,of a system configured to convert carbon-containing materials to fuel inaccordance with embodiments of the invention;

FIG. 1C is a diagram of a tilted reaction chamber system in accordancewith embodiments of the invention;

FIG. 1D is a diagram of a side view of a reaction chamber system inaccordance with embodiments of the invention;

FIG. 2A is a block diagram of a system that uses the reaction chambersystems illustrated in FIGS. 1A and 1B for water/air extraction and areaction process in accordance with embodiments of the invention;

FIG. 2B illustrates a reaction system that includes feedback control inaccordance with embodiments of the invention;

FIG. 3A shows system which includes multiple stationary magnetronsarranged on a drum that is disposed outside a cylindrical reactionchamber having one or more microwave-transparent walls;

FIG. 3B illustrates a system having a drum supporting magnetrons whichmay be rotated around the longitudinal axis of the reaction chamberwhile the reaction chamber is concurrently rotated around itslongitudinal axis;

FIG. 3C shows a reaction chamber with a feedstock transport mechanismcomprising baffles;

FIG. 4 illustrates a system having a rotating magnetron in addition to asecondary heat source;

FIG. 5 depicts a system wherein a magnetron is moved along thelongitudinal axis of the reaction chamber and is rotated around thelongitudinal axis of the reaction chamber; and

FIG. 6 is a flow diagram of a process for generating fuel fromcarbon-containing feedstock in accordance with embodiments of theinvention.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail below. It is to be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the invention isintended to cover all modifications, equivalents, and alternativesfalling within the scope of the invention as defined by the appendedclaims.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

In the following description of the illustrated embodiments, referencesare made to the accompanying drawings forming a part hereof, and inwhich are shown by way of illustration, various embodiments by which theinvention may be practiced. It is to be understood that otherembodiments may be utilized, and structural and functional changes maybe made without departing from the scope of the present invention.

The following description relates to approaches for processing gas,solid and/or liquid carbon-containing feedstock into fuels, e.g., dieselfuels, gasoline, kerosene, etc., by thermally and/or microwave enhancedreaction processes, including depolymerization, polymerization, reactivechemistry, isomerization, etc. For example, depolymerization may becaused by heating or by exposure to microwaves. Depolymerization, alsoreferred to as “cracking”, is a refining process that uses heat to breakdown (or “crack”) hydrocarbon molecules into shorter polymer chainswhich are useful as fuels. Depolymerization and other reaction processesmay be enhanced by adding a catalyst to the feedstock which increasesthe speed of the reaction and/or reduces the temperature and/or theradiation exposure required for the processes. Furthermore, thecatalyst, such as zeolite, has a nanostructure which allows onlymolecules of a certain size to enter the crystalline grid or activatethe surface areas of the catalyst and to interact with the catalyst.Thus, the catalyst advantageously is very effective at controlling theproduct produced by the reaction processes because only substanceshaving a specified chain length may be produced using the catalyticprocess. Catalytic depolymerization is particularly useful fortransforming biomass and other carbon-containing feedstock into fuelsuseable as transportation or heating fuels.

Any thermal and/or radiation driven fuel production techniques can beachieved using the methodologies and/or systems of the disclosedembodiments. Some of the examples provided herein are based ondepolymerization processes, however, these are non-limiting in that theyare provided as illustrations of the invention. Embodiments of theinvention are also applicable to other processes of reactive chemistry,e.g., polymerization, isomerization.

One aspect of efficient depolymerization (and other reactions) is theability to heat and/or irradiate the feedstock substantially uniformlyto the temperature that is sufficient to cause depolymerization as wellas activate the catalyst. Upon depolymerization, long hydrocarbon chains“crack” into shorter chains. Microwave heating has been shown to beparticularly useful in heating systems for thermal depolymerization.Heating systems such as flame, steam, and/or electrical resistiveheating, heat the feedstock by thermal conduction through the reactionchamber wall. These heating systems operate to heat the feedstock fromthe outside of the reaction chamber walls to the inside of thefeedstock, whereas microwaves heat from the inside of the feedstocktoward the reaction chamber walls. Using non-microwave heating sources,the heat is transferred from the heat source outside wall to the insideof the vessel wall that is in direct contact with the feedstock mixture.The heat is then transferred to the surfaces of the feedstock and thentransferred, again, through the feedstock until the internal areas ofthe feedstock are at a temperature near the temperature of the reactionchamber wall.

One problem with this type of external heating is that there are timelags between vessel wall temperature transmission and raising thefeedstock temperature that is contained in the center of the vessel aswell as the internal area of the feedstock matrix. Mixing the feedstockhelps to mitigate these conditions. Still, millions of microenvironmentsexist within the reactor vessel environment and the feedstock particlesthemselves. This causes uneven heat distribution within the reactionchamber of varying degrees. These variant temperature gradients causeuncontrollable side reactions to occur as well as degradation of earlyconversion products that become over-reacted because of the delay inconversion reaction timeliness. It is desirable to produce and retainconsistent heating throughout the feedstock and the reaction products sothat good conversion economics are achieved and controllable. Microwaveheating is an efficient heating method and it also serves to activatecatalytic sites.

Embodiments of the invention are directed to a reaction chamber systemthat can be used to process any carbon-containing feedstock, whethergas, solid and/or liquid, to extract the volatile organic compounds inthe feedstock at a temperature range that will produce transportationfuels. The reaction chamber can also act in a reactive mode that willconvert gaseous carbon feedstock into different gaseous chemicalspecies. The system involves a heating system that enhances uniformheating and/or microwave irradiation throughout the feedstock, therebyincreasing the efficiency of the reaction.

Some reaction chamber systems described herein use microwave heating toachieve more uniform temperature within the feedstock, and, as a result,a more efficient reaction. Microwaves are absorbed by the watermolecules in the material that is irradiated in the microwave. When thewater molecules absorb the microwaves, the molecules vibrate, whichcreates heat by friction, and the heat is convected to the surroundingmaterial.

The reason microwaves are absorbed by water molecules is specific to thecovalent bonds that attach the hydrogen to the oxygen in a watermolecule. The oxygen atom in water has a large electronegativityassociated with it due to the size of its nucleus in comparison to thehydrogen atom and the electrons from the two hydrogen atoms are drawncloser to the oxygen atom. This gives this end of the molecule a slightnegative charge and the two hydrogen atoms then have a slight positivecharge. The consequence of this distortion is that the water moleculeacts like a small, weak magnet. The dipole feature of the water moleculeallows the molecule to absorb the microwave radiation and starts itvibrating like a guitar string. The vibration of the bonds causesfriction that turns to heat and then spreads out into the irradiatedmaterial.

To take advantage of this feature of microwave radiation, a reactionchamber system described herein takes advantage of microwave irradiationand/or heating in processing feedstock that contains carbon and can beconverted to transportation fuels. The reactor may be made from asubstantially microwave transparent substance such as quartz, aglass-like material that is substantially transparent to microwaveradiation. Because quartz can be manipulated into many shapes, itprovides design discretion for shaping the reaction chamber, but in oneexample the reaction chamber is configured in the shape of a tube orcylinder. The cylindrical shape allows for the feedstock to feed in oneend and exit at the opposite end. An example of a suitable reactionchamber would be a quartz tube that is about four feet long with a wallthickness of 3/16″.

Microwave radiation is generated by a magnetron or other suitabledevice. One or more microwave producing devices, e.g., magnetrons can bemounted external to the quartz tube wall. Magnetrons come in differentpower ranges and can be controlled by computers to irradiate theprocessing feedstock with the proper energy to convert the feedstock tomost desirable fuel products efficiently. In one application, themagnetron can be mounted on a cage that would rotate around the outsideof the reactor tube as well as travel the length of the reactor tube.Feedstock traveling through the length of the inside of the tube will betraveling in a plug flow configuration and can be irradiated by fixedand/or rotating magnetrons. A computer may be used to control the powerand/or other parameters of the microwave radiation so that differentfeedstock, with different sizes and densities can be irradiated atdifferent parameter settings specific to the feedstock and thus convertthe feedstock more efficiently.

These configurations of a reactor will allow efficient processing offeedstocks, from relatively pure feedstock streams to mixed feedstockstreams that include feedstocks of different densities, moisturecontents, and chemical make up. Efficiencies can occur because the fuelproducts are extracted from the reactor chamber as they are vaporizedfrom the feedstock, but further processing of the remaining feedstockoccurs until different fuel products are vaporized and extracted. Forexample, dense feedstock, such as plastics, take longer to process intoa useable fuel than less dense feedstock, such as foam or wood chips.The system described herein continues to process dense feedstock withoutover-processing the earlier converted products from the less densefeedstock. This is accomplished by using both stationary and rotatingmicrowave generators.

One example of a mixed feedstock would be unsorted municipal solidwaste. In some implementations, catalyst may be added in the feedstockwhich helps in the conversion of the feedstock as well as the speed atwhich the conversion can progress. A catalyst can be designed to reactat the preset processing temperature inside the reactor or to react withthe impinging microwave radiation. In some embodiments, no catalyst isrequired. In other embodiments, the catalyst may be a rationallydesigned catalyst for a specific feedstock.

The plug flow configuration with the reactors described herein willallow adjustments to the residence time that the feedstock resideswithin the reactor core for more efficient exposure to the heat and theradiation of the microwaves to produce the desired end products.

Inlets and/or outlets, e.g., quartz inlets and/or outlets can be placedalong the walls of the reaction chamber to allow for pressure and/orvacuum control. The inlets and outlets may allow the introduction ofinert gases, reactive gases and/or the extraction of product gases.

Thus, the design of the microwave-transparent reaction chamber, the useof microwaves as a heating and/or radiation source with fixed and/orrotating magnetrons, plug flow processing control, with or without theuse of catalysts, will allow the processing of any carbon-containingfeedstock in any physical phase.

A system in accordance with embodiments of the invention includes areaction chamber having one or more substantially microwave-transparentwalls and a microwave heating/radiation system. The microwaveheating/radiation system is arranged so that microwaves generated by theheating/radiation system are directed through the substantiallymicrowave-transparent walls of the reaction chamber and into thereaction cavity where the feedstock material is reacted withoutsubstantially heating the walls of the reaction chamber. To enhance thetemperature uniformity of the feedstock, the reaction chamber and theheating/radiation system may be in relative motion, e.g., relativerotational and/or translational motion. In some implementations, theheating system may rotate around a stationary reaction chamber. In someimplementations, the feedstock within the reaction chamber may rotate bythe use of flights with the heating/radiation system remainingstationary. In some implementations, the reaction chamber may rotatewith the heating system remaining stationary. In yet otherimplementations, both the reaction chamber and the heating/radiationsystem may rotate, e.g., in countercurrent, opposing directions. Tofurther increase temperature uniformity, the system may include amechanism for stirring and/or mixing the feedstock material within thereaction chamber. The reaction chamber may be tilted during reactionprocess, for example, to force the feedstock to go through the catalyticbed.

FIGS. 1A and 1B illustrate side and cross sectional views, respectively,of a system 100 for converting carbon-containing feedstock to fuel inaccordance with embodiments of the invention. Although the reactionchamber 110 may be any suitable shape, the reaction chamber 110 isillustrated in FIGS. 1A and 1B as a cylinder having a cylindrical wall111 that is substantially transparent to microwaves in the frequencyrange and energy used for the reaction process. The reaction chamber 110includes a reaction cavity 112 enclosed by the cylindrical wall 111. Thesystem 100 includes a transport mechanism 118 configured to move thefeedstock through the reaction chamber. The operation of the system 100with regard to the reactions taking place within the reaction chamber110 may be modeled similarly to that of a plug flow reactor.

As illustrated in FIG. 1A, system includes a transport mechanism 118 formoving the feedstock material through the reaction chamber 110. Thetransport mechanism 118 is illustrated as a screw auger, although othersuitable mechanisms, e.g., conveyer, may also be used. The transportmechanism 118 may further provide for mixing the feedstock within thereaction chamber. In some embodiments, the reaction chamber wall 111 mayhave a thickness of about 3/16 inches. The smoothness of the reactionchamber wall 111 facilitates the movement of the feedstock through thereaction chamber 110.

A heating/radiation subsystem 115 may include any type of heating and/orradiation sources, but preferably includes a microwave generator 116such as a magnetron which is configured to emit microwaves 113 having afrequency and energy sufficient to heat the carbon-containing feedstockto a temperature sufficient to facilitate the desired reaction of thefeedstock, for example, for depolymerization of the feedstock,microwaves in a frequency range of about 0.3 GHz to about 300 GHz may beused. For example, the operating power of the magnetrons may be in therange of about 1 Watt to 500 kilowatts. The magnetron 116 is positionedin relation to the reaction chamber 110 so that the microwaves 113 aredirected through the wall 111 of the reaction chamber 110 and into thereaction cavity 112 to heat and/or irradiate the material therein. Amechanism 117 provides relative motion between the magnetron 116 and thereaction chamber 110 along and/or around the longitudinal axis 120 ofthe reaction chamber 110. In some embodiments, the mechanism 117 mayfacilitate tilting the reaction chamber 110 and/or the magnetron 116 atan angle θ (FIG. 1C) to facilitate the reaction of the feedstock and/orthe extraction of gases, for example. In the embodiment illustrated inFIGS. 1A-C, the magnetron 116 is positioned on a rotational mechanism117, such as a rotatable cage or drum, that rotates the magnetron 116around the stationary reaction chamber 110. In some implementations, therotation around the chamber may not be complete, but the rotation pathmay define an arc around the circumference of the reaction chamber. Therotation may occur back and forth along the path of the arc. Aspreviously mentioned, in some embodiments, the reaction chamber 110 maybe the rotating component, or both the heating/radiation subsystem 116and the reaction chamber 110 may rotate, e.g., in opposing,countercurrent directions. The rotation between the reaction chamber andthe magnetron provides more even heating and more even microwaveexposure of the feedstock within the reaction cavity 112, thus enhancingthe efficient reaction chemistry of the feedstock and/or other processesthat are temperature/radiation dependent, such as removal of water fromthe feedstock. The rotation lessens the temperature gradient and/ormaintains a more constant microwave flux across the plug inside thereaction chamber.

The reaction chamber 110 may include one or more entry ports 120, e.g.,quartz entry ports, configured to allow the injection or extraction ofsubstances into the reaction cavity 112. In one implementation, thequartz ports may be used to extract air and/or oxygen from the reactioncavity. Extraction of air and/or oxygen may be used to suppresscombustion which is desirable for some processes.

For example, in certain embodiments, the system 100 may be used topreprocess the feedstock through compression and/or removal of airand/or water. In this application, gases such as hydrogen and/ornitrogen may be injected through one or more ports 120 to hydrogenateand/or suppress combustion of the feedstock. The reaction chamber 110may also include one or more exit ports 121, e.g., quartz exit ports,configured to allow passage of water, water vapor, air, oxygen and/orother substances and/or by-products from the reaction chamber 110.

FIG. 1D is a diagram illustrating a reaction chamber system 150 forproducing fuel from carbon-containing feedstock in accordance withembodiments of the invention. The system 150 includes an input hopper(also referred to as a load hopper) 151 configured to allow introductionof the feedstock material into the system 150. A gearmotor auger drive152 provides a drive system for the auger 153 that transports thefeedstock through the system 150. As the feedstock is compressed in theload hopper 151, air is extracted through the atmosphere outlet 154. Aseal 155 isolates the load hopper 151 from the reaction chamber 156 tomaintain a level of vacuum. The reaction chamber 156 includes walls of amicrowave-transparent material. One or more stationary microwave heads157 are positioned at the walls of the reaction chamber 156. Inaddition, the system 150 includes one or more rotating microwave heads158. In one implementation, each rotating microwave head is located at afixed position with respect the longitudinal axis 160 of the reactionchamber 156. The rotating microwave head is mounted on a slipringbearing 159 which allows the microwave head 158 to rotate around thereaction chamber 156. In some implementations the rotating microwavehead(s) 158 may rotate around the longitudinal axis 160 of the reactionchamber 156 as well as moving back and forth along the longitudinal axis160. The system 150 includes a seal at the exit of the reaction chamber156 to maintain the reaction chamber vacuum.

FIG. 2A is a block diagram of a system 200 that uses one or more of thereaction chamber systems 100 illustrated in FIGS. 1A and 1B. Thereaction chamber systems 220, 230 may be arranged and/or operated inseries or in a parallel configuration. The extraction process 220 andthe reaction process 230 depicted in FIGS. 2A and 2B are illustrated asoccurring in two separate reaction chambers, e.g., that operate atdifferent temperatures. Alternatively, the extraction process and thereaction process may be implemented in a single reaction chamber withtwo separate zones, e.g., two separate temperature zones.

In the system 200 of FIG. 2, one or both of the water/air extractionsubsystem 220 and the reaction subsystem 230 may be similar to thereaction chamber system 100 of FIGS. 1A and 1B. Carbon-containingfeedstock, such as manure, wood chips, plant-based cellulose, tires,municipal solid waste, enters the system through a hopper 211, andtraverses an airlock 212 to enter a feedstock preparation module 213. Ifneeded, a catalyst, such as zeolite, and/or other additives that enhancethe reaction process, for example to adjust the pH, may be introducedinto the system 200 through the input hopper 211 and/or the entry ports(shown in FIG. 1B). In the feedstock preparation module 213, thefeedstock material is shredded to a predetermined particle size may bedependent on the properties of the feedstock, such as the purity,density, and/or chemical composition of the feedstock. If used, thecatalyst may be added at the time that the feedstock is being preparedso that the catalyst is evenly dispersed within the feedstock materialbefore entering the reaction chamber 231. In general, the less uniformthe feedstock, the smaller the particle size needed to provide efficientreaction.

After the initial feedstock preparation stage, the shredded and mixedfeedstock is transported by a transport mechanism 215 into the reactionchamber 221 of the next stage of the process. The air/water extractionsubsystem 220, which performs the optional processes of water and/orextraction prior to the reaction process, has similarity to the systemillustrated in FIGS. 1A and 1B, includes a heating/radiation module 222comprising at least a magnetron 223 configured to generate microwaves226 which may be mounted on a rotational or stationary mechanism 227. Ifmounted on a rotational mechanism, the mechanism rotates the magnetron223 either partially or fully around the reaction chamber 221 as themicrowaves 226 are directed through the wall 224 of the reaction chamber221 and into the reaction cavity 225 impinging on and heating thefeedstock therein. In some embodiments, the heating module 222 mayutilize only one magnetron 223 or only two or more magnetrons withoutusing other heat/radiation sources.

In some embodiments, the heating/radiation module 222 may utilize themagnetron 223 in addition to other heat sources, such as heat sourcesthat rely on thermal conduction through the wall of the reactionchamber, e.g., flame, steam, electrical resistive heating, recycled heatfrom the process, and/or other heat sources. During the air and/or waterextraction process, the feedstock may be heated to at least 100 C, theboiling point of water, to remove excess water from the feedstock. Theexcess water (e.g., in the form of steam) and/or other substances mayexit the reaction chamber 221 via one or more exit ports. Additives tothe feedstock, such as inert and/or reactive gases including hydrogenand/or nitrogen, may be introduced via one or more input ports into thereaction chamber 221 of the water/air extraction process. In addition tobeing heated and/or irradiated by microwaves, the feedstock may also besubjected to a pressurized atmosphere and/or a vacuum atmosphere and/ormay be mechanically compressed to remove air from the reaction chamber221.

After the optional air and/or water extraction process, the transportmechanism 215 moves the feedstock to the next processing stage 230 whichinvolves the reaction process, e.g., thermal depolymerization, of thefeedstock. After the feedstock/catalyst mixture enters the reactionchamber 231, it is heated to a temperature that is sufficient tofacilitate the desired reaction. For example, to produce diesel fuelthrough depolymerization, a temperature of in a range of about 20° C. toabout 35° C. is used to crack the hydrocarbons in the feedstock intoshorter chains. In addition to being heated, the feedstock may also besubjected to a pressurized atmosphere, a vacuum atmosphere and/or may bemechanically compressed in the reaction chamber 231.

In some embodiments, heating/radiation in the reaction chamber 231 isaccomplished using a magnetron 233 emitting microwaves 236. Themagnetron 233 may rotate relative to the reaction chamber 231. Aspreviously described in connection with the water extraction stage 220,the rotating magnetron 233 may be supported by rotational mechanism 237,such as a cage or drum. The rotational mechanism 237 allows relativerotational motion between the magnetron 233 and the reaction chamber231. For example, the magnetron 233 may rotate completely around thereaction chamber 231 or the rotation of the magnetron 233 may proceedback and forth along an arc that follows the circumference of thereaction chamber 231. The rotating magnetron heating system 233 may besupplemented using a stationary magnetron, and/or other conventionalheat sources such as a flame or electrical resistive heating. Rotatingthe magnetron 233 provides more even heating/radiation of the feedstockmaterial and catalyst within the reaction cavity 235 and enhances theheating properties over that of stationary heat sources.

The cracked hydrocarbons vaporize and are collected in a condenser 241and liquefy and then are sent to the distiller 240 to the diesel fuel,while heavier, longer chain hydrocarbon molecules may be recycled backto the reaction chamber. In some implementations, distillation may notbe necessary, and the fuel product only needs to be filtered. In someconfigurations, it is desirable to control the processes of the reactionto allow a higher efficiency of fuel extraction from the feedstock. FIG.2B is a block diagram of a system 205 that includes the systemcomponents described in connection with FIG. 2A along with a feedbackcontrol system 250. The illustrated feedback control system 250 includesa controller 251 and one or more sensors 252, 253, 254 which may beconfigured to sense parameters at various stages during the process. Thefeedback control system 250 may include sensors 252 at the feedstockpreparation stage which are configured to sense parameters of thefeedstock and/or feedstock preparation process. For example, the sensors252, may sense the chemical composition of the feedstock, density,moisture content, particle size, energy content or other feedstockparameters. The sensors 252 may additionally or alternatively sense theconditions within the feedstock preparation chamber, e.g., flow,pressure, temperature, humidity, composition of the gases present in thechamber, etc. The sensors 252 develop signals 255 a which are input tothe controller electronics 251 where they are analyzed to determine thecondition of the feedstock and/or the feedstock preparation process. Inresponse to the sensed signals 255 a, the controller 251 developsfeedback signals 255 b which control the operation of the feedstockpreparation module 213. For example, in some implementations, thecontroller 251 may control the feedstock preparation module 213 tocontinue to shred and/or grind the feedstock material until apredetermined particle size and/or a predetermined particle sizevariation is detected. In another example, based on the sensed chemicalcomposition of the feedstock, the controller 251 may cause a greater orlesser amount of catalyst to be mixed with the feedstock or may causedifferent types of catalyst to be mixed with the feedstock.

The control system 250 may also develop feedback signals 256 b, 257 b tocontrol the operation of the water extraction module 220 and/or thereaction module 230, respectively, based on sensed signals 256 a, 257 a.For example, the sensors 253, 254 may sense the temperature of the waterextraction and/or reaction processes and the controller 251 may developfeedback signals 256 b, 257 b to control the operation of theheating/radiation systems 222, 232, e.g., power, frequency, pulse width,rotational or translational velocity, etc. of one or both of themagnetrons 223, 233. The controller 251 may develop feedback signals tothe magnetrons to control the amount of radiation impinging on thefeedstock so that the feedstock will not be over- or under-cooked anddevelopment of hot spots will be avoided. The controller 250 may controlthe injection of various substances into one or both of the extractionchamber and/or the reaction chamber 221, 231 through the entry ports tocontrol the processes taking place within the chambers 221, 231. Theresidue of the depleted feedstock (char) is sent to a storage unit.After the distillation stage, the heavy hydrocarbons may be recycledback into the reaction chamber and the lighter hydrocarbons may be senton to a polymerization stage.

As previously discussed, the reaction chambers may be made of quartz,glass, ceramic, plastic, and/or any other suitable material that issubstantially transparent to microwaves in the frequency and energyrange of the reaction processes. In some configurations, theheating/radiation systems described herein may include one or moremagnetrons that rotate relative to the reaction chamber. In someembodiments, the magnetrons may be multiple and/or may be stationary.FIG. 3A illustrates system 300 which includes multiple stationarymagnetrons 311 arranged on a drum 312 that is disposed outside acylindrical reaction chamber 313 having one or moremicrowave-transparent walls. The operation of the magnetrons may becontinuous, or may be pulsed, e.g., in a multiplexed pattern. In someembodiments (FIG. 3B), the drum 312 supporting the magnetrons 311 may berotated 320 around the longitudinal axis 350 of the reaction chamber 313and/or the reaction chamber 313 may be rotated 330 around itslongitudinal axis 350.

A feedstock transport mechanism may be disposed within the reactionchamber. For example, as illustrated in FIG. 3C, the feedstock transportmechanism may comprise one or more baffles 361 that are configured tomove the feedstock through the reaction chamber 360 as the reactionchamber rotates. The baffles 361 may be mounted to the walls of thereaction chamber 360 and/or may be otherwise installed within thereaction chamber to provide movement of feedstock within and through thereaction chamber 360, e.g., longitudinally through the reaction chamber.

In some embodiments, illustrated in FIG. 4, one or more secondary heatsources 450, such as a flame, steam, and/or electric resistive heating,or recycled heat, may be used in addition to magnetrons 416 which arestationary, or are supported on a mechanism 417 that rotates around thecircumference of the reaction chamber 420. In some configurations, themagnetrons 416 may not make a complete revolution around the reactionchamber 420, but may rotate back and forth 419 along an arc that followsthe circumference of the reaction chamber 420.

Movement of the one or more magnetrons relative to the reaction chambermay also include motion that moves the magnetron along the longitudinalaxis of the reaction chamber, as illustrated in FIG. 5. FIG. 5illustrates a reaction chamber 510 and a cage 520 that supports amagnetron 530. The cage 520 and magnetron 530 may be moved 540 back andforth along the longitudinal axis 550 of the reaction chamber 510. Insome implementations, in addition to and/or concurrent with the motion540 of the cage 520 and magnetron 530 along the longitudinal axis 550,the cage 520 and magnetron 530 may be rotated 560 around thelongitudinal axis 550.

FIG. 6 is a flow chart illustrating a process for producing fuel from acarbon-containing feedstock in accordance with embodiments of theinvention. A carbon-containing feedstock, such as biomass, municipalsolid waste, plant material, wood chips and the like is input 610 to areaction chamber having walls that are substantially transparent tomicrowaves used to heat and/or irradiate the feedstock. The feedstockmay be a gas, liquid and/or solid matter. The heating and/or radiationoccurs by directing 620 the microwave energy through the walls of thereaction chamber so that it impinges on the feedstock disposed withinthe reaction chamber. The feedstock is heated/irradiated 630 by themicrowaves, optionally in the presence of a catalyst, until reaction ofthe carbon-containing molecules occurs to produce the desirable end fuelproduct. The fuel product created by the reaction processes arecollected 640.

Various modifications and additions can be made to the preferredembodiments discussed hereinabove without departing from the scope ofthe present invention. Accordingly, the scope of the present inventionshould not be limited by the particular embodiments described above, butshould be defined only by the claims set forth below and equivalentsthereof.

What is claimed is:
 1. A system for producing fuel from acarbon-containing feedstock, comprising: a first reaction chambercomprising a first microwave-transparent chamber wall and a firstreaction cavity configured to hold the carbon-containing feedstock andhaving a steam exit port; a second reaction chamber, separate from thefirst reaction chamber, the second reaction chamber comprising a secondmicrowave-transparent chamber wall and a second reaction cavityconfigured to hold the carbon-containing feedstock; a microwavesubsystem comprising at least one microwave device configured to emitmicrowaves when energized, the microwave device positioned relative tothe first and second reaction chambers so that the microwaves aredirected through the first and second microwave-transparent chamberwalls and into the first and second reaction cavities, respectively; amechanism configured to provide relative motion between the microwavedevice and at least one of the first and second reaction chambers; and amotor-driven feedstock transport mechanism configured to mechanicallycompress the carbon-containing feedstock in the first reaction chamberand to move the carbon-containing feedstock into the second reactionchamber; wherein the microwave subsystem is configured to cause themicrowave device to heat the carbon-containing feedstock in the firstreaction chamber to a first temperature of about 100° C. while steamexits from the first reaction chamber via the steam exit port and toheat the carbon-containing feedstock in the second reaction chamber to asecond temperature, different from the first temperature, and whereinthe system is configured so that reactions in the first and secondreaction chambers convert the carbon-containing feedstock to atransportation fuel product at an output of the system.